The B-47E (Model 450-157-35) was the major production version of the Stratojet. It was the only version that was mass-produced by all three members of the Stratojet production pool--a total of 1341 B-47Es were built--386 by Lockheed, 264 by Douglas, and 691 by Boeing.
The B-47E was basically the standardized production version of the Stratojet, and incorporated many innovations that had been suggested by experience with the B-47B. It standardized on six General Electric J47-GE-25 engines, which offered a thrust of 7200 pounds with water injection. These engines had already been refitted to several B-47Bs. The 18-unit internal JATO system was retained on early models, but was soon replaced by a jettisonable rack that contained 33 1000 lb.s.t units that could be dropped following takeoff. The B-47E was fitted from the start with an approach chute to increase drag and a brake chute to decrease the landing roll. An anti-skid braking device was also fitted.
The defensive armament was changed to two 20-mm cannon in the tail. The A-5 fire control system that had taken so long to develop was finally fitted. The A-5 fire control system was much better than the discarded B-4 system of earlier versions, and could automatically detect and track pursuing aircraft and aim and fire the 20-mm cannon. The earlier B-4 system could at best spray machine gun fire in the general direction of an attacking plane, without much prospect of actually scoring a hit.
The B-47E incorporated as standard equipment an inflight refuelling receptacle for flying-boom midair refuelling on the starboard side of the nose. The use of inflight-refuelling capability enabled the total fuel capacity to be reduced to 14,610 gallons, including two 1700-gallon drop tanks carried underneath the wings between the engine nacelles.
The crew was finally provided with ejector seats as standard equipment, with the pilot and copilot ejecting upward over the tail and the bombardier/navigator ejecting downward through a hatch in the lower nose.
The undersurfaces and lower portion of the fuselage of most B-47Es were painted a glossy white to reflect the heat radiation from nuclear blasts. This reflective paint was applied retroactively to some B-47Bs.
During FY 1953 production, a clamshell cockpit canopy was introduced, hinged on the right side.
The first B-47E flew on January 30, 1953, and the Air Force accepted this plane in February. By mid-year, 127 similar production examples had been delivered. The first B-47Es went in April 1953 to the 303rd Medium Bomb Wing based at Davis Monthan AFB in Arizona. The next recipient of the B-47E was the 22nd Wing at March AFB in California, retiring their B-47Bs to the Air Training Command.
By mid 1953, peak B-47 procurement was expected to reach almost 2200, but was cut by 140 in September 1953. A further production cut of 200 aircraft considered in October was prevented in favor of a 20-month production stretchout during the period in which the B-52 production line was getting up to speed. In contrast to the B-36 program, which was on the verge of cancellation several times, there was never any significant effort to cancel the B-47 program.
The B-47E rapidly became the dominant component of the USAF strategic deterrent during the mid- and late-1950s. By December of 1953, SAC had 8 B-47 Medium Bomber Wings. In December 1954, the SAC inventory counted 17 fully-equipped B-47 wings. By the beginning of 1956, 22 medium bombing wings had received the B-47, and another 5 wings were getting ready to convert to the B-47. In December 1956, SAC had 27 combat-ready B-47 wings, with 1204 combat-ready B-47 crews and 1306 B-47 aircraft assigned.
Progressive modifications resulted in four sub-variants of the B-47E.
The first of these, designated B-47E-I, introduced water/alcohol-injected J-47-GE-25A engines, rated at 7200 lb/st each. Phase II ECM equipment was provided, denoted by a small circular antenna on the rear fuselage. Maximum takeoff weight was 200,000 pounds.
A modified landing gear allowing heavier takeoff weights appeared on the 521st and subsequent B-47Es, and this configuration was labeled B-47E-II. Other modifications included the addition of Phase III ECM gear, which consisted of an AN-ALT-6 jammer mounted in a bulged fairing underneath the rear fuselage and antennae housed in wingtip extensions. The first B-47E-II reached the Air Force in August of 1953.
The B-47E-III introduced a three-phase electrical power supply
A far stronger landing gear was incorporated on the 862nd and later B-47E. This configuration was known as B-47E-IV. The IV also introduced a series of electronics upgrades including the MA-7A bombing radar, the AN/ASP-54 warning radar, and the AN/APG-39 gun-laying radar. The B-47E-IV had a takeoff weight of 230,000 pounds, 28,000 pounds more than previously permissible. This extra weight was largely devoted to extra fuel, enabling the combat radius of the IV to increase to 2050 nautical miles, almost twice the distance demonstrated 5 years earlier by the first B-47A. The maximum warload was 25,000 pounds.
The Air Force received its first B-47E-IV in February 1955. In March of 1955, it was decided that all active B-47s would be brought up to the IV standard.
Spurred by the Suez crisis of 1956, SAC demonstrated its ability to launch a large striking force on short notice when in December more than 1000 B-47s flew nonstop, simulated combat missions, averaging 8000 miles each over the American continent and Arctic regions.
Early in 1955, the Strategic Air Command requested the B-47 be adapted for low-level bombing, with the aircraft delivering its bomb via the toss-bomb technique. In a toss-bombing attack, the plane enters the run at low altitude, pulls up sharply into a half loop with a half roll on top and releases the bomb at a predetermined point in the climb. The bomb continues upward in a high arc, falling on the target at a considerable distance from its release point. In the meantime, the maneuver allows the airplane to reverse its direction and gives it more time to speed away to a safe distance from the blast. This technique was adopted because it was thought that high-speed B-47s flying at low level would be less vulnerable to enemy countermeasures. The existence of low-level capable B-47s would mean that a potential enemy would now be faced with threats from both high- and low-level attacks.
In June of 1955, a 6000-pound dummy bomb was successfully released from a B-47E during a 2.6g pullup from level flight. In another test flight, an 8850-pound practice bomb was dropped from a 2.5-g pullup. Despite some doubts about the structural integrity of the B-47 under the stresses involved in such maneuvers, in December 1955 SAC ordered that 125 B-47s be modified for low-level flight.
Low-level bombing involved special crew training. A training program known as Hairclipper was started in December of 1955. However, adverse weather, excessive maintenance requirements, serious deficiencies in LABS systems, and several accidents caused Hairclipper to be officially discontinued in March of 1958. However, the end of Hairclipper did not signify the end of low-level flying. A program known as Pop Up, a related training program that took advantage of recent advances in weapons developments, fared better. In the Pop Up maneuver, the aircraft came it low level, pulled up to high altitude, released its weapon, and then dove steeply to escape being spotted by enemy radars. Following the discovery of fatigue cracks in the wings of some B-47s in April of 1958, Pop Up was interrupted while the entire B-47 fleet could be checked. It was resumed in September, and by the end of 1959 the training program had finally been completed.
On January 25, 1957, a B-47 flew from March AFB, California to Hanscom Field, Massachusetts in 3 hours, 47 minutes, at an average speed of 710 mph (assisted by strong tailwinds). On August 14, 1957, a 321st Bomb Wing B-47 made a record nonstop flight from Andersen AFB, Guam to Sidi Slimane Air Base in French Morocco, a distance of 11,450 miles in 22 hours and 50 minutes. This required 4 midair refuellings. In November of 1959, a B-47 assigned to the Wright Air Development Center stayed in the air for 3 days 8 hours 36 minutes, covering 39,000 miles. This broke previous time-and-distance records.
The discovery of fatigue cracks in the wings of the B-47 during April of 1958 and a rash of new accidents in early 1958 triggered an immense inspection and repair program known as Milk Bottle. All three B-47 manufacturers as well as the AMC were involved in Milk Bottle. The low-level B-47s of the 306th and 22nd Bomb Wings were the first to enter the program, since they were most in danger of fatigue cracking. The program ended in July of 1959. Although Milk Bottle did not solve all the B-47's problems, it did go a long way in making operations with the B-47 a lot safer.
SAC initially wanted 1000 B-47s modified for low-level flying, which meant fitting virtually the entire Stratojet fleet with absolute altimeters, terrain-avoidance equipment, and Doppler radar. Because of the Milk Bottle repair program, testing delays, and the phaseout of some SAC B-47 wings due to a lack of funds, SAC was forced to scale down its low-altitude requirements to only 500 Stratojets. This program was given a new sense of urgency by the belief that by 1963 all B-47s would be hopelessly obsolete if they were not equipped for low-level flight. However, fund shortages dictated that SAC scale down its low-altitude requirements to only 350 aircraft.
A total of 691 B-47Es were built by Boeing-Wichita, Douglas-Tulsa built 264, and Lockheed-Marietta built 386. The final B-47E (53-6244) was delivered in 1957 to the 40th Bomb Wing, 44th Bomb Squadron at Schilling AFB in Salina, Kanses. 53-6244 was transfered to Lincoln AFB, Nebraska where it remained until it was transfered to the USAF Museum at Wright Patterson AFB, Ohio. Reports that 53-6244 served at Pease AFB are incorrect.
The beginning of the phaseout of the B-47E coincided with the delivery of the last example. In 1957, the 93rd Bomb Wing started exchanging its B-47s for B-52s. In March of 1961, President John F. Kennedy directed that the phaseout of the B-47 be accelerated. However this was delayed in July by the onset of the Berlin crisis of 1961-62. In the following years, B-47s were gradually delivered to the storage facility at Davis-Monthan AFB. SAC's last two B-47s went to storage on February 11, 1966.
51-2357/2411 Boeing B-47E-55-BW Stratojet (55) Model 450-157-35, c/n 450410/450464 2358,2360,2362,2363,2366,2369,2373,2375, 2380,2383,2385,2387,2390,2396,2397,2402, 2406,2408 converted to WB-47E 2360 on display at New England Air Museum 51-2412/2445 Boeing B-47E-60-BW Stratojet (34) Model 450-157-35, c/n 450465/450498 2412/2415,1417,2420,2427,2435 converted to WB-47E 51-5214/5234 Boeing B-47E-60-BW Stratojet (21) Model 450-157-35, c/n 450499/450519 5219,5220 converted to YDB-47E for Rascal program 5218,5257 converted to WB-47E 51-5235/5257 Boeing B-47E-65-BW Stratojet (23) Model 450-157-35, c/n 450520/450542 51-7019/7050 Boeing B-47E-65-BW Stratojet (32) Model 450-157-35, c/n 450562/450593 7021,7046,7049 to WB-47E 51-7051/7064 Boeing B-47E-70-BW Stratojet (14) Model 450-157-35, c/n 450594/450607 7058, 7063 to WB-47E 51-7065/7083 Boeing B-47E-75-BW Stratojet (19) Model 450-157-35, c/n 450608/450626 7066 to WB-47E 51-15804/15810 Lockheed-Marietta B-47E-5-LM Stratojet (7) 51-15811/15812 Lockheed-Marietta B-47E-10-LM Stratojet (2) 51-17368/17386 Boeing B-47E-75-BW Stratojet (19) Model 450-158-36, c/n 450660/450678 52-0019/0028 Douglas-Tulsa B-47E-1-DT Stratojet (10) c/n 43637/43643 52-029/041 Douglas-Tulsa B-47E-5-DT Stratojet (13) c/n 43644/43656 52-042/058 Douglas-Tulsa B-47E-10-DT Stratojet (17) c/n 43657/43669, 43751/43754 52-059/081 Douglas-Tulsa B-47E-15-DT Stratojet (23) c/n 43755/43777 52-082/111 Douglas-Tulsa B-47E-20-DT Stratojet (30) c/n 43778/43807 52-112/120 Douglas-Tulsa B-47E-25-DT Stratojet (9) c/n 43808/43816 52-146/176 Douglas-Tulsa B-47E-25-DT Stratojet (31) c/n 44000/44030 0166 on display at Castle AFB Museum 52-177/201 Douglas-Tulsa B-47E-30-DT Stratojet (25) c/n 44031/44055 52-202/207 Lockheed-Marietta B-47E-10-LM Stratojet (6) 52-208/220 Lockheed-Marietta B-47E-15-LM Stratojet (13) 52-221/235 Lockheed-Marietta B-47E-20-LM Stratojet (15) 52-236/260 Lockheed-Marietta B-47E-25-LM Stratojet (25) 52-261/292 Lockheed-Marietta B-47E-30-LM Stratojet (32) 52-293/330 Lockheed-Marietta B-47E-35-LM Stratojet (38) 0305 converted to EB-47L 52-331/362 Lockheed-Marietta B-47E-40-LM Stratojet (32) 52-363/393 Lockheed-Marietta B-47E-45-LM Stratojet (31) 0389 to JB-47E 52-394/431 Boeing B-47E-80-BW Stratojet (38) Model 450-157-35, c/n 450679/450716 52-432/469 Boeing B-47E-85-BW Stratojet (38) Model 450-157-35, c/n 450717/450754 52-470/507 Boeing B-47E-90-BW Stratojet (38) Model 450-157-35, c/n 450755/450792 52-508/545 Boeing B-47E-95-BW Stratojet (38) Model 450-157-35, c/n 450793/450830 52-546/583 Boeing B-47E-100-BW Stratojet (38) Model 450-157-35, c/n 450831/450868 52-584/620 Boeing B-47E-105-BW Stratojet (37) Model 450-157-35, c/n 450869/450905 52-621/684 Cancelled contract for B-47E Stratojet 52-1406/1417 Douglas-Tulsa B-47E-35-DT Stratojet (12) c/n 44090/44101 52-3343/3373 Lockheed B-47E-50-LM Stratojet (31) 53-1819/1849 Lockheed-Marietta B-47E-55-LM Stratojet (31) 53-1850/1880 Lockheed-Marietta B-47E-60-LM Stratojet (31) 53-1881/1911 Lockheed-Marietta B-47E-65-LM Stratojet (31) 53-1912/1942 Lockheed-Marietta B-47E-70-LM Stratojet (31) 53-1943/1972 Lockheed-Marietta B-47E-55-LM Stratojet (30) 53-1973/2027 cancelled contract for B-47E 53-2028/2040 Douglas-Tulsa B-47E-35-DT Stratojet (13) c/n 44149/44161 53-2041/2089 Douglas-Tulsa B-47E-DT Stratojet - all cancelled 53-2090/2103 Douglas-Tulsa B-47E-40-DT Stratojet (14) c/n 44436/44449 53-2104/2117 Douglas-Tulsa B-47E-45-DT Stratojet (14) c/n 44450/44463 53-2118/2131 Douglas-Tulsa B-47E-50-DT Stratojet (14) c/n 44464/44477 53-2132/2144 Douglas-Tulsa B-47E-55-DT Stratojet (13) c/n 44478/44490 53-2145/2157 Douglas-Tulsa B-47E-60-DT Stratojet (13) c/n 44491/44503 53-2158/2170 Douglas-Tulsa B-47E-65-DT Stratojet (13) c/n 44504/44516 53-2171/2260 Boeing B-47E-BW Stratojet - all cancelled 53-2261/2296 Boeing B-47E-110-BW Stratojet (36) Model 450-157-35, c/n 4501074/4501109 2280 on display at WPAFB Museum 53-2297/2331 Boeing B-47E-115-BW Stratojet (35) Model 450-157-35, c/n 4501110/4501144 53-2332/2367 Boeing B-47E-120-BW Stratojet (36) Model 450-157-35, c/n 4501145/4501180 2345,2346 to DB-47E 53-2368/2402 Boeing B-47E-125-BW Stratojet (35) Model 450-157-35, c/n 4501181/4501215 53-2403/2417 Boeing B-47E-130-BW Stratojet (15) Model 450-157-35, c/n 4501216/4501230 53-4207/4244 Boeing B-47E-130-BW Stratojet (38) Model 450-157-35, c/n 4501231/4501268 some converted to ETB-47E and EB-47L 53-6193/6244 Boeing B-47E-135-BW Stratojet (52) Model 450-157-35, c/n 4501334/4501385 some converted to ETB-47E and EB-47L
Engines: Six General Electric J47-GE-25 turbojets, 5970 lb.s.t dry and 7200 lb.s.t. with water injection. Performance: Maximum speed 607 mph at 16,300 feet, 557 mph at 38,500 feet. Cruising speed 500 mph. Stalling speed 175 mph. Service ceiling 33,100 feet, combat ceiling 40,500 feet. Combat climb rate 4660 feet per minute (maximum power). Combat radius 2013 miles with 10,845 pound bombload . 4035 miles ferry range withy 16,318 gallon fuel load. Takeoff ground run 10,400 feet, 7350 feet with JATO. Dimensions: Wingspan 116 feet 0 inches, length 107 feet 0 inches, height 27 feet 11 inches, wing area 1428 square feet. Weights: 79,074 pounds empty, 133,030 pounds combat, 198,180 pounds gross, 230,000 pounds maximum takeoff. Armament: Two 20-mm M24A1 cannon in extreme tail. Maximum bombload 25,000 pounds.